Portable building



FIG. 1 is a perspective view of the portable building showing my new design;

FIG. 2 is a side view of the portable building of FIG. 1;

FIG. 3 is an end view of the portable building of FIG. 1;

FIG. 4 is a top view of the portable building of FIG. 1; and,

FIG. 5 another perspective view of the portable building taken from an alternate angle.

The broken line showing in the Figures is for the purpose of illustrating the portable building and forms no part of the claimed design. 

The ornamental design for a portable building, as shown and described. 